Intermetallic coatings produced by TIG surface melting

The titanium aluminide intermetallic alloys possess high specific strength, high hardness and high temperature capabilities up to 800 degreesC such as corrosion and oxidation resistance. These alloys can be suitable replacements for the conventional ceramic coatings applied in many components of chemical plants and aircraft engines to protect against high temperature oxidation and corrosion. The initial feasibility study of the forming of intermetallic alloy coatings on titanium surfaces was undertaken using powder preplacement and TIG surface melting processes. The present paper describes the process parameters that are associated with this route of formation of intermetallic alloy coatings and other issues that include the ability to achieve a defect-free uniform intermetallic layer with superior mechanical properties, and constitutional and microstructural uniformity across the section. The alloy coatings were characterised in terms of microstructures, defects. wear, and hardness using microscope, microhardness tester, tribometer and XRD. Melting conditions were optimised to produce Ti3Al and TiAl coatings without any pores, cavities and cracking. The coating layers yielded a hardness of over 500 HV. (C) 2001 Elsevier Science B.V. All rights reserved.